KLK3 and prostate neoplasm: In general, patients with organ-confined PCa are initially treated with radical prostatectomy or radiation-based therapies; however, 25–40% of patients will experience biochemical recurrence defined by a rise in prostate-specific antigen (PSA), an androgen-regulated gene which in these patients acts as a biomarker of recurrent prostate tumour growth and metastatic progression [32].